When coal is burned in thermal power plants, it releases several types of emissions. One of the primary emissions is Carbon dioxide (CO2), which is a result of the combustion of the carbon present in the coal. In addition to this, the combustion process also results in the formation of Oxides of Nitrogen (NOx) and Oxides of Sulphur (SOx). These are formed due to the reaction of nitrogen and sulphur present in the coal with oxygen in the air. Therefore, all three - Carbon dioxide, Oxides of Nitrogen, and Oxides of Sulphur - are emissions from coal combustion at thermal power plants.